OFDM (orthogonal frequency division multiplexing), having a simple equalizer, is resistant to multi-path fading, and has thus recently been widely used in wireless communication. OFDM has been adopted to be used in various wireless communication systems such as a wireless local area network (WLAN), a wireless metropolitan area network (WMAN), digital audio broadcasting (DAB), and digital video broadcasting (DVB).
However, in general, an OFDM signal has a very high peak-to-average power ratio (PAPR) in a transmitter. Such a high PAPR causes a transmission apparatus based on OFDM to be very sensitive to non-linear distortion caused by a power amplifier (PA). Without sufficient backoff with respect to power, a frequency spectrum of a system broadens and distortion is generated due to inter-frequency modulation to result in degradation of system performance.
Thus, PAPR may be reduced to 0 dB by combining OFDM modulation and angle modulation. Such a modulation scheme is called constant envelope orthogonal frequency division multiplexing (CD-OFDM). The CE-OFDM scheme satisfies OFDM characteristics to be resistant to multi-path facing and has a uniform amplitude.